1. Field of the Invention
The invention relates to a cooling device for a projector, and particularly to a cooling device that direct hot air directly into fan blades to reduce temperature of fan hub.
2. Description of the Prior Art
Please refer to FIG. 1 that illustrates a prior art of projector 10, comprising a light source 121 of a light unit 12 inside a casing 11, the light source 121 creating a high-brightness and high-contrast projecting light ray 122 when acted on by an optical engine 13m. A light cut 123 installed on the upper side of the light unit 12 to obstruct the light source 121 of the light unit 12. In the prior art, heated air is subject to the action of a first fan 157, air entering the projector 10 through a first air inlet window 151 becomes a first hot current 153, which after passing a first printed circuit board 141 is separated into a third hot current 155 and a fourth hot current 156. The third hot current 155 passing a first fan 157 and fan blades 1572 is exhausted out of the projector 10, and the fourth hot current 156 is directed through the third fan 162 into the light source heat exhausting unit 16. On the other hand, when subjected to action by the second fan 158, air enters through the second air inlet window 152 into the projector 10, creating a second hot current 154. The second hot current 154 respectively passes an optical engine 13, a second printed circuit board 142 and a light unit 12, then through a plurality of fan blades 1582 of the second fan 158, finally out of the projector 10.
Due to the action of the second fan 158, the fourth hot current 156 directed through the third fan 162 into the light source heat exhausting unit 16 passes an air duct 161 to absorb the heat generated by the light source 121, so the temperature of the fourth hot current 156 rises rapidly. After passing the light cut 123, the fourth hot current 156 in the prior art of projector 10 is squarely aligned with the second fan 158, then the second hot current 154 is exhausted out of the projector 10 by the action of the fan blades 1582 of the second fan 158.
A shortcoming in the prior art of projector 10 lies in that the heat radiating direction of the fourth hot current 156 is squarely in alignment with the second fan 158 or the second fan hub 1581. The heat generated by the light source 121 of the light unit 12 is the highest in the projector 10, so the heat carried by the fourth hot current 156 after passing the light cut 123 is also the highest. Accordingly, when the fourth hot current 156 exhaust heat directly against the second fan hub 1581, the heat will be collected at the front of the second fan hub 1581 before it passes a plurality of second fan blades 1582 and out of the projector 10, forming a higher average temperature at the front of the second fan hub 1581. As shown in FIG. 5, when the prior art of the projector 10 is operating under room temperature using a light source 12 of approximately 130 Watt, the air temperature at 1 mm position 159 to the front of the center of the second fan hub 1581 will reach as high as 206.6 degrees Fahrenheit, which is higher than the maximum operating temperature of 194 degrees Fahrenheit for the second fan 158, resulting in adverse effects to the motor bearings, control circuits, rotors, stators and such key components in the hub of the second fan 158, thereby reducing the working life and reliability of the second fan 158.
As shown in FIG. 2 that illustrates another prior art of projector 20, comprising a casing 21, a light unit 22, a light source 221, an optical engine 23, a light cut 223, a first printed circuit board 241, a second printed circuit board 242, a cooling device 25, a first air inlet window 251, a second air inlet window 252, a first fan 257, a light source heat exhausting unit 26, a third fan 262, an air outlet 263 and an air inlet 261, which are the same as the first prior art, but different in that the second fan 258, the fan hub 2581 and the fan blades 2582 are installed at a rear part of the light source 221. It has the shortcoming that the heat carried by the fourth hot current 256 is also the highest. As a result, when heat is exhausted in a lower right direction from a specified distance between the fourth hot current 256 and the second fan 258, the heat will be collected at the front of the second fan hub 2581 before passing the second fan blades 2582 and out of the projector 20, forming a higher average temperature at the front of the second fan hub 2581, bringing adverse effects to the motor bearings, control circuits, rotors, stators and such key components in the second fan hub 2581, reducing the working life and reliability of the second fan 258 and the prior art of the projector 20.
The objective of the invention is to provide a cooling device for projector, to direct hot current directly into fan blades, thereby reducing the temperature of the fan hub, and increasing the working life and reliability of the product.
To achieve the above objective, the present invention involves a light source that provides light to the projector device. With an air duct extending from the light source to a second exhaust fan, so air in the vicinity of the light source is exhausted through the second fan blades and out of the projector, wherein the second exhaust fan comprises a second fan hub and a plurality of second fan blades, the second fan hub being located at a center of the second exhaust fan, the second fan blades respectively connected to a periphery of the second fan hub, thereby the air in the vicinity of the second fan blades in the projector is exhausted through the second fan blades and out of the projector. The air duct is in a closed status at the periphery of the light source, concentrating a direction for exhaustion, and the air outlet is squarely aligned with the second fan blades.